Preparation method of anode active material for pseudocapacitor

Abstract

The present disclosure provides a method of preparing an anode active material having high specific capacitance in a simple and inexpensive process without applying high temperature and high pressure conditions by synthesizing urchin-shaped goethite iron oxide (alpha-FeOOH) using an aqueous solution containing thiosulfate ions and sulfate ions, followed by heat treatment to synthesize hematite iron oxide (alpha-Fe 2 O 3 ) having a nano-sized urchin-like structure, in order to provide an anode for a pseudocapacitor that is excellent in specific capacitance.

The invention claimed is: 
     
       1. A preparation method of an anode active material, comprising the steps of:
 preparing a mixed solution by mixing a precursor material of iron oxide and a C1 to C18 alcohol-based compound, followed by adding an aqueous solution containing thiosulfate ions and sulfate ions; 
 reacting the mixed solution at a temperature of 50° C. to 75° C. to prepare goethite iron oxide (alpha-FeOOH); and 
 heat treating the goethite iron oxide (alpha-FeOOH) at a temperature of 250° C. to 400° C. to prepare hematite iron oxide (alpha-Fe 2 O 3 ). 
 
     
     
       2. The preparation method of an anode active material according to  claim 1 ,
 wherein the precursor material of iron oxide is at least one selected from the group consisting of iron chloride (FeCl 3 .6H 2 O), iron nitrate (Fe(NO 3 ) 3 .9H 2 O), iron sulfate (Fe 2 (SO 4 ) 3 .xH 2 O), iron bromide (FeBr 3 ), iron perchlorate (Fe(ClO 4 ) 3 ), and iron phosphate (FePO 4 ). 
 
     
     
       3. The preparation method of an anode active material according to  claim 1 ,
 wherein the thiosulfate ion is derived from at least one compound selected from the group consisting of sodium thiosulfate (Na 2 S 2 O 3 ), potassium thiosulfate (K 2 S 2 O 3 ), and barium thiosulfate (BaS 2 O 3 ). 
 
     
     
       4. The preparation method of an anode active material according to  claim 1 ,
 wherein the sulfate ions are derived from at least one compound selected from the group consisting of sodium sulfate (Na 2 SO 4 ), lithium sulfate (Li 2 SO 4 ), ammonium sulfate ((NH 4 ) 2 SO 4 ), and potassium sulfate (K 2 SO 4 ). 
 
     
     
       5. The preparation method of an anode active material according to  claim 1 ,
 wherein the alcohol-based compound is at least one selected from the group consisting of methanol, ethanol, propanol, and isopropanol. 
 
     
     
       6. The preparation method of an anode active material according to  claim 1 ,
 wherein a concentration of the mixed solution containing the precursor material of iron oxide is 20 mM to 100 mM. 
 
     
     
       7. The preparation method of an anode active material according to  claim 1 ,
 wherein a concentration of the aqueous solution containing thiosulfate ions and sulfate ions is 40 mM to 200 mM in total of the thiosulfate ions and the sulfate ions. 
 
     
     
       8. The preparation method of an anode active material according to  claim 1 ,
 wherein a stoichiometric ratio of the precursor of iron oxide and a sum of the thiosulfate ions and the sulfate ions is 1:1 to 1:7 based on the precursor of iron oxide. 
 
     
     
       9. The preparation method of an anode active material according to  claim 1 ,
 wherein the thiosulfate ion is contained in a stoichiometric ratio of 1:1 to 1:4 based on the precursor of iron oxide. 
 
     
     
       10. The preparation method of an anode active material according to  claim 1 ,
 wherein the hematite iron oxide (alpha-Fe 2 O 3 ) has an urchin-like structure in which nanorods are aggregated. 
 
     
     
       11. The preparation method of an anode active material according to  claim 10 ,
 wherein the nanorods have a diameter of 10 nm to 200 nm and a length of 300 nm to 1000 nm. 
 
     
     
       12. The preparation method of an anode active material according to  claim 10 ,
 wherein the hematite iron oxide (alpha-Fe 2 O 3 ) has a number average particle diameter of 0.6 micrometers to 2 micrometers. 
 
     
     
       13. The preparation method of an anode active material for the pseudocapacitor according to  claim 1 , wherein the hematite iron oxide (alpha-Fe 2 O 3 ) has a specific surface area of 40 m 2 /g or more. 
     
     
       14. The preparation method of an anode active material according to  claim 1 , wherein:
 preparing the mixed solution comprises mixing iron chloride (FeCl 3 .6H 2 O), iron nitrate (Fe(NO 3 ) 3 .9H 2 O), or a mixture thereof with methanol, ethanol, or a mixture thereof, and then adding an aqueous solution containing sodium thiosulfate (Na 2 S 2 O 3 ) and sodium sulfate (Na 2 SO 4 ), lithium sulfate (Li 2 SO 4 ), or a mixture thereof; 
 reacting the mixed solution reacting at a temperature of 68° C. to 72° C. for 4 hours to 6 hours to prepare goethite iron oxide (alpha-FeOOH); and 
 heat treating the goethite iron oxide (alpha-FeOOH) comprising heating at a temperature of 250° C. to 400° C. for 2 to 4 hours to prepare hematite iron oxide (alpha-Fe 2 O 3 ). 
 
     
     
       15. An anode composition for a pseudocapacitor, comprising the hematite iron oxide (alpha-Fe 2 O 3 ) prepared by the method according to  claim 1  as an active material. 
     
     
       16. The anode composition for the pseudocapacitor according to  claim 15 ,
 wherein specific capacitance measured by cyclic voltammetry is 300 F/g or more in a 1 M KOH electrolyte.